This is the revision C version of the Shaft2 module.

Shaft2 Module (Revision C)

1. Introduction
2. Programming
3. Hardware
- 3.1 Circuit Schematic
- 3.2 Printed Circuit Board
4. Software
5. Issues

1. Introduction

The Shaft2 module keeps track of two quadrature rotation sensors.

2. Programming

Command
Name Bit Action Description
8 7 6 5 4 3 2 1 0

Count Latch 0 0 0 0 0 0 0 0 0 Send Latch the current rotation count for both shafts.

Count Clear 0 0 0 0 0 0 0 0 1 Send Clear rotation count for both shafts.

Read Shaft 0 0 0 0 0 0 0 1 s Send Read the latched 16-bit shaft value for shaft s. Return the high order 8 bits as hhhh hhhh. Save the low order 8 bits for the Read Shaft Continue command.
0 h h h h h h h h Send

Read Shaft Continue 0 0 0 0 0 0 1 0 0 Send Return the low order 8 bits of the last shaft read as llll llll.
0 l l l l l l l l Send

Common
Commands 0 1 1 1 1 1 1 x x Send Standard common command. See specifications for details.
0 a a a a a a a a Receive

Select 1 a a a a a a a a Send Select the module with an address of aaaa aaaa. A time-out indicates that the module is not selected. (FIXME: 0xa5 is currently returned.)
0 0 0 0 0 0 0 0 0 Receive

Command Name	Bit	Action	Description
8	7	6	5	4	3	2	1	0
Count Latch	0	0	0	0	0	0	0	0	0	Send	Latch the current rotation count for both shafts.
Count Clear	0	0	0	0	0	0	0	0	1	Send	Clear rotation count for both shafts.
Read Shaft	0	0	0	0	0	0	0	1	s	Send	Read the latched 16-bit shaft value for shaft s. Return the high order 8 bits as hhhh hhhh. Save the low order 8 bits for the Read Shaft Continue command.
0	h	h	h	h	h	h	h	h	Send
Read Shaft Continue	0	0	0	0	0	0	1	0	0	Send	Return the low order 8 bits of the last shaft read as llll llll.
0	l	l	l	l	l	l	l	l	Send
Common Commands	0	1	1	1	1	1	1	x	x	Send	Standard common command. See specifications for details.
0	a	a	a	a	a	a	a	a	Receive
Select	1	a	a	a	a	a	a	a	a	Send	Select the module with an address of aaaa aaaa. A time-out indicates that the module is not selected. (FIXME: 0xa5 is currently returned.)
0	0	0	0	0	0	0	0	0	Receive

3. Hardware

The hardware consists of a circuit schematic and a printed circuit board.

3.1 Circuit Schematic

The parts list kept in a separate file -- shaft2.ptl.

The schematic for the Shaft2 module is shown below:

3.2 Printed Circuit Board

The printed circuit board files are listed below:

shaft2_back.png: The solder side layer.
shaft2_front.png: The component side layer.
shaft2_artwork.png: The artwork layer.
shaft2.gbl: The RS-274X "Gerber" back (solder side) layer.
shaft2.gtl: The RS-274X "Gerber" top (component side) layer.
shaft2.gal: The RS-274X "Gerber" artwork layer.
shaft2.gml: The RS-274X "Gerber" mask layer.
shaft2.drl: The "Excellon" NC drill file.
shaft2.tol: The "Excellon" tool rack file.

4. Software

The following files are available:

shaft2.ucl: The Shaft2 µCL source code file.
shaft2.asm: The Shaft2 firmware assembly code listing.
shaft2.lst: The Shaft2 firmware listing file.
shaft2.hex: The Shaft2 firmware Intel^® Hex file.

5. Issues

The following fabrication issues came up:

The spec. sheet suggest that each crystal have two load capacitors and a load resistor. There is not enough space. However, the non-quadrature count mode does not need the crystals and works just fine. Perhaps the device will work with resonators instead.
The pin numbers on the 1×5 headers are reversed.